The Bypass Angioplasty Revascularization Investigation (BARI) is a randomized, multicenter, clinical trial that compares a strategy of initial percutaneous transluminal coronary angioplasty (PTCA) to that of initial coronary artery bypass surgery (CABG) for selected patients with multivessel coronary artery disease. The primary hypothesis tested is that a strategy of initial PTCA is no worse than one of initial CABG with respect to mortality at five years. Other major endpoints include: myocardial infarction, need for repeat procedures and hospitalizations, functional status, radionuclide ejection fraction, quality of life and economic impact. Coronary and LV angiography were obtained at study entry on all 1829 randomized patients, 2013 registry patients and 422 angiographically ineligible patients. The Central Radiographic Core Laboratory (CRL) has been responsible for interpreting LV and coronary angiograms acquired at study entry, during PTCA procedures, during five year follow-up and those required in a one-year angiography sub-project. CRL has been responsible for quality control of all angiographic procedures performed in BARI, assisting PTCA operator certification and interpretation of all cineangiographic films. Collection of angiography data in electronically coded formats for subsequent transfer to the Data Coordinating Center(DCC) has been facilitated by use of a distributed computerized angiographic data acquisition system at all clinical sites and at CRL. CRL has completed interpretation of all entry and initial PTCA angiography and is currently reading intercurrent procedures as they occur. This request for extended angiographic follow-up of intercurrent procedures is based on the fact that 10% of patients in the randomized and angiographically excluded cohorts have procedures during each year of follow-up. Availability of angiographic findings during extended follow-up permits one to assess the extent to which failure of revascularization therapy or progression of native coronary disease is responsible for clinical events (e.g.. infarction, angina, exercise test ischemia). Moreover, the extent to which repeat PTCA procedures are related to restenosis or new lesion development can be evaluated. BARU is the largest and most comprehensive study comparing PTCA and CABG, thus providing a wealth of angiographic data to be correlated with clinical outcomes and the opportunity to evaluate the extent to which angiographic features of individual lesions prior to and following angioplasty are predictive of clinical and angiographic outcomes during extended patient follow-up. Data analyses incorporating angiographic results are supported by CRL development of complex algorithms that measure the extent of coronary disease and semi-quantitatively estimate the amount of LV myocardial jeopardy. CRL angiographic analyses, when correlated with the clinical results of BARI, are an important component in interpreting the results BARI.